Biomedical subjects

E Khor

Publications and source records attributed to E Khor.

27 records · Page 2Linked to original sources

PubMed1996

Prevention of prosthetic valve endocarditis by impregnation of gentamicin into surgical pledgets.

A novel drug delivery system was developed for the treatment of prosthetic valve endocarditis (PVE). The antibiotic, gentamicin, was impregnated into surgical pledgets using non-solvent coacervation of polylactic acid (PLA) as a binding/encapsulating agent. The in vitro dissolution profiles show controlled release of gentamicin for up to 36 h when PLA of molecular weight 2000 is used and up to 7 d for PLA with a molecular weight of 50,000. The results indicate potential for the localized treatment of PVE, which is cost-effective, easy to manufacture and permits dosage variability.

Anti-Bacterial Agents↗

PubMed1996

Animal tissue-polypyrrole hybrid biomaterials: shrinkage temperature evaluation.

The shrinkage temperature of animal tissue-polypyrrole hybrids have been evaluated. The results indicate that the tissue's shrinkage temperature behaviour is retained. The tissues do not appear to have been affected by surface layering with polypyrrole or poly(sodium 3-pyrrolyl-butanesulphonate) (PSPBS). The main influence on the shrinkage temperature appears to be the reaction conditions in producing the hybrids i.e. the solvent and the presence of FeCl3. Hybrids obtained from reactions where the solvent was acetic acid demonstrated irreversible denaturation giving a final lower shrinkage temperature than the original value. All tissues exposed to FeCl3 were found to have higher shrinkage temperatures. This has been attributed to transient coordination bonding between the metal ion and side groups on the amino acid. The single peak of PSPBS-tissue hybrids in acetic acid is probably associated with the effective penetration of the PSPBS into the tissue, permitting some interaction between the functionalities of the conducting polymer and collagen.

Alkanesulfonic Acids↗

PubMed1996

Hybrid biomaterials based on the interaction of polyurethane oligomers with porcine pericardium.

Hybrid biomaterials have been produced by the interaction of polyurethane oligomers with both fresh and glutaraldehyde-fixed porcine pericardium. The hybrid biomaterials so formed were translucent with occasional white streaks and/or spots, had increased stiffness (to touch) but remained pliable. No shrinkage temperature was detected for fresh porcine pericardium hybrid up to 100 degrees C compared to porcine pericardium (approximately 67 degrees C) and glutaraldehyde-fixed porcine pericardium (approximately 87 degrees C). Amino acid analysis of the fresh porcine pericardium hybrid showed a reduction in lysine content after active isocyanate-terminated polyurethane oligomers exposure, indicating cross-linking between the polymer and tissue. Histological examination of the hybrid material shows a thin grey coating on both surfaces of the tissue, implying at least surface cross-linking of the tissue with polyurethane. The results suggest that fresh porcine pericardium can be reacted with active isocyanate-terminated polyurethane oligomers to produce hybrid biomaterials with covalent bonding.

Animals↗

PubMed1996

Promotion of calcification on carboxymethylchitin discs.

A series of water-insoluble carboxymethylchitin (CM-chitin) discs of varying degrees of substitution (d.s.) has been investigated for their interaction with calcium phosphate. Discs of d.s. 0.03, 0.11, 0.14 and 0.23 were prepared by casting from solutions of CM-chitin in 90% formic acid. Calcium uptake and calcium phosphate nucleation were found to increase with the degree of substitution of the CM-chitin discs. The results suggest that water-insoluble CM-chitin may be useful as a platform for in vivo calcification.

Analysis of Variance↗

PubMed1995

Validation of the shrinkage temperature of animal tissue for bioprosthetic heart valve application by differential scanning calorimetry.

Shrinkage temperature is most often used to report the degree of cross-linking in glutaraldehyde-fixed animal tissue for use in bioprosthetic heart valve fabrication. Present practice utilizes the measurement of hydrothermal shrinkage observed when a sample is subjected to a temperature programme. This measurement at best gives a general indication of the efficiency of the treatment, i.e. the extent of cross-linking in the tissue. When differential scanning calorimetry has been used, the ambiguity arising from the scant reporting of the protocols used does not permit easy comparison of experimental results. This report addresses the considerations necessary to obtain optimum results in the differential scanning calorimetry experiment for the determination of shrinkage temperature in biological tissue. The shrinkage temperature of two previously unreported tissue types, porcine pericardium and equine pericardium, are provided and compared with those of bovine pericardium and porcine aortic valve leaflets.

Animals↗

PubMed1995

In situ polymerization of pyrrole in animal tissue in the formation of hybrid biomaterials.

Porcine pericardium was impregnated with pyrrole or its derivative, sodium 4-(3-pyrrolyl)butanesulphonate (SPBS), by soaking the animal tissue in the monomer. Subsequent in situ chemical polymerization of the monomer-rich tissue using FeCl3 as initiator produced black polypyrrole-tissue hybrid biomaterials. The rate and extent of polymerization was found to be greater in 0.5 M acetic acid than in Hepes-buffered saline (HBS) and also greater for SPBS than for pyrrole. However, better tissue integrity was obtained for polymerization in HBS. Histological examination showed that the monomers do not permeate through the entire tissue, restricting polymerization to the surface layers of the tissue. The samples so formed do not exhibit detectable electrical conductivity.

Acetates↗

PubMed1993

Trivalent metal ions in the prevention of calcification in glutaraldehyde treated biological tissues. Is there a chemical correlation?

The influence of chemical factors on trivalent metal ions in the prevention of calcification of glutaraldehyde treated biological tissue has been explored. The results indicate that the chemical link lies in the hard character of the trivalent metal ions. Metal ions with the hardest character appear to have the best chance of reacting with oxygen atoms of the phosphate groups at nucleation sites of hydroxyapatite. This disrupts the nucleation and thus prevents calcification in glutaraldehyde treated biological tissue.

Animals↗

PubMed1993

Non-invasive magnetic resonance imaging of the soft tissue response to a biomaterial.

Magnetic resonance imaging (MRI) has been employed to visualize the tissue response to hydrogel implants in rats. High contrast MR images of the implant site were obtained. Distinct tissue variations in the MR images have been observed. These can be attributed to either the surgical procedure or the application of a tissue irritant to produce inflammation and have been verified histologically. This study demonstrates that MRI is potentially a useful tool for the non-invasive in-vivo evaluation of biomaterials.

Animals↗

PubMedDate not supplied

Fluoride release and antibacterial properties of new-generation tooth-colored restoratives.

The aim of this study was to compare the amounts and pattern of fluoride release and antibacterial properties of new-generation restoratives over a 35-day period. Materials evaluated included fluoride-releasing composites (Tetric, Experimental X), compomers (Dyract, Compoglass), and a resin-modified glass-ionomer cement (Fuji II LC). A conventional glass ionomer (Fuji II Cap) was used as a control for fluoride-release testing. Five samples of each restorative material were evaluated for daily fluoride release over a 35-day period by means of ion chromatography. Ranking of materials from least to greatest total fluoride release over 35 days was as follows: Tetric < Experimental X < Dyract < Fuji II LC < Compoglass < Fuji II Cap. Fuji II Cap had significantly greater fluoride release than all other materials evaluated. Fuji II Cap, Fuji II LC, and Compoglass had similar patterns of fluoride release characterized by a high initial release that was many times that released later. The fluoride-releasing composites evaluated stopped releasing fluoride by day 14. Antibacterial testing was conducted using the agar diffusion inhibitory test. Five samples of each restorative were assessed at baseline and weekly intervals up to 35 days. The microorganisms used were Lactobacillus casei, Streptococcus mutans, and Streptococcus sobrinus. IRM, a zinc oxide/eugenol cement, was used as the baseline control. None of the restorative materials evaluated affected the growth of L casei, S sobrinus, or S mutans at all time periods including baseline, where fluoride was detected in the agar beneath the specimen disks. There was no correlation noted between fluoride-release potential and antibacterial properties.

Anti-Infective Agents, Local↗